1. Field of the Invention
The present invention relates to an electrical rotary machine of a permanent magnet type in complex with permanent magnets, and particularly, to a permanent magnet type electrical rotary machine with high torque, high power, and enhanced reliability in a limited space.
2. Description of Related Art
Recent years have observed remarkable researches and developments in the art of permanent magnet, having developed permanent magnets with a high magnetic energy product, involving advancements in miniaturization and power enhancement of electrical rotary machines. In particular, for electrical rotary machines having such applications to vehicles as addressed to hybrid automobiles, there have been desiderata for higher efficiencies for enhanced fuel consumption, as well as for controlled gas emission. Further, for desirable increase in torque and enhancement of power to be achieved in a limited space in a narrow place for installation, there have been desiderata for increased quantities of permanent magnet, as well as for higher speeds. Accordingly, there has been a desideratum for rotor core strength along with high centrifugal forces, besides a desideratum for reduction of motor loss in consideration of occurrences of a thermal issue due to an increased density of loss.
FIG. 1 shows configuration of a rotor 10 of a permanent-magnet reluctance electrical rotary machine according to a related art. The rotor 10 has a rotor core 8 and a set of permanent magnets 2. The rotor core 8 is made to be easy of magnetization in a direction, and difficult in another direction. In other words, the rotor core 8 is configured for formation of magnetic unevenness, with a lamination of magnetic steel sheets that has permanent magnet implanting slots 1 for implanting permanent magnets 2, eight in number, in the direction of easy magnetization. The eight permanent magnet implanting slots 1 are arranged in a crossing relationship for formation of four salient poles. Namely, permanent magnet implanting slots 1 paired to be located at both sides of a nonmagnetic portion 3 have an interleaved portion therebetween as an interpolar portion that forms a magnetopolar recess. Further, in the permanent magnet implanting slots 1, there are arranged permanent magnets 2 magnetized so as to cancel magnetic flux of armature currents intersecting magnetic flux passing through magnetic pole portions to produce reluctance torque. That is, for permanent magnets 2 residing at both sides of a magnetic pole portion, their magnetization directions have identical senses to each other, and for permanent magnets 2 paired to be located at both sides of an interpolar portion, their magnetization directions have mutually opposite senses in a circumferential direction of the rotor 10.
In FIG. 1, there are illustrated lines of magnetic flux φd as a component of magnetic flux by armature currents with respect to d (direct)-axis in the direction along a magnetopolar axis of rotor core 8. In this direction, the core of magnetic pole portion constitutes a flux path. This magnetic path has a very small reluctance, and provides a magnetic configuration with a tendency for magnetic flux to travel.
FIG. 2 illustrates lines of magnetic flux φq as a component of magnetic flux by armature currents with respect to q (quadrature)-axis in the direction along an interconnecting axis between a center of the rotor 10 and a central part of an interpolar portion. Magnetic flux φq passing through the interpolar portion is produced along such a magnetic path that traverses an associated nonmagnetic portion 3 and permanent magnets 2 at both sides of the interpolar portion. The nonmagnetic portion 3 has a relative magnetic permeability of “1”, and the permanent magnets 2 have a relative magnetic permeability of approximately “1”, as well. As a result, magnetic flux φq by armature currents is reduced by the effect of high magnetic resistances.
Interlinking magnetic flux φm of permanent magnets 2 has an opposing distribution to the magnetic flux φq as a component of magnetic flux by armature currents with respect to q-axis in the direction of an interpolar center axis, and repulses magnetic flux φq by armature currents invading through an associated interpolar portion, canceling each other. At the interpolar air gaps, the density of air-gap flux produced by armature currents is reduced by magnetic flux φm of permanent magnets 2, and is greatly changed in comparison with the density of air-gap flux at the magnetic poles. That is, for the position of rotor 10, the air-gap flux density has a great change, involving a great change of magnetic energy. Further, there is a magnetic portion 11 that may magnetically short at the boundary between magnetic pole and interpolar section under a loaded condition, with a tendency to get magnetically strong saturated by load currents. The interpolar distribution of magnetic flux by permanent magnets 2 is thereby increased. The air-gap flux distribution thus has uneven profiles greatly changed by such magnetic flux and magnetic resistances of permanent magnets 2, thus involving significant great changes of magnetic energy, allowing for great output.
FIG. 3 shows a rotor configuration of a permanent-magnet reluctance electrical rotary machine disclosed in Japanese Patent Application Laid-Open Publication No. 2001-339919. A rotor core 8 has a part interleaved between permanent magnet implanting slots 1 located at both sides of a nonmagnetic portion 3, as an interpolar portion forming a magnetic recess. In the permanent magnet implanting slots 1, there are arranged permanent magnets 2 magnetized so as to cancel magnetic flux of armature currents intersecting magnetic flux passing through magnetic pole portions to produce reluctance torque. A nonmagnetic portion 3 is made by an air gap.
In the rotor core 8, each permanent magnet implanting slot 1 has a pair of permanent magnet positioning projections 4 projecting inside the slot. The permanent magnet positioning projections 4 have, at the bases, their R-cut (escaping) parts 5 provided on the planer side crossing a magnetizing direction of permanent magnet 2 at right angles, in opposition to the nonmagnetic portion 3.
Provision of such permanent magnet positioning projections 4 allows the permanent magnets 2 to be supported with secured degrees of strength at thinned portions (outer circumferential thinned parts 6, thinned bridging parts 7) where stresses are concentrated, to thereby afford an increased power output and higher speed. Further, the R-cut parts are thereby allowed to have a minimized value of stress, allowing for an increased revolution speed and enhanced reliability.
FIG. 4 is an enlarged radial sectional view depicting details in part of a rotor 10 of a permanent-magnet reluctance electrical rotary machine disclosed in Japanese Patent Application Laid-Open Publication No. 2001-339922. As shown in FIG. 4, the rotor 10 has a cavity 9 arranged in an interpolar q-axis direction to be difficult for magnetic flux to travel, and is configured so as to meet a relationship, such that:PL/2πRWqave≧130where P is the number of poles, L [m] is a circumferential width of the cavity 9, R [m] is a radius of the rotor 10, and Wqave [m] is an average of thickness Wq of a rotor core 8 along an outer side of the cavity 9 in a radial direction of the rotor.
Such being the case, the permanent-magnet reluctance electrical rotary machine of FIG. 4 has a cavity 9 (interpolar air gap) disposed at an outer circumferential side of permanent magnets 2 arranged in a V-form, with its configuration and dimensions being numerically limited to afford high torque, thereby enabling an increased power output and speed-variable operation.